Ask the Expert: Social Security's ex-factor

You must be at your full retirement age to get your spousal benefit but postpone your own. If you're younger, you're automatically applying for both benefits, and you get the larger of the two. But you can apply within three months of your birthday, as long as you make it very clear you don't want your spousal benefit to begin until your birthday month, says Jane Zanca, a Social Security Administration spokeswoman.

Your age isn't the only eligibility requirement. Your marriage must have lasted at least 10 years, you must be currently unmarried, and your ex-husband must already be eligible to claim Social Security. He doesn't need to have applied for it yet; that would only be a requirement if you were still married to him.

Call the Social Security Administration (800-772-1234) for an appointment at a local field office. Bring your marriage certificate and divorce decree, proof of your age, U.S. citizenship or legal residence and a photo ID.

A birth certificate and a passport or a driver's license should do it. You must provide your ex-husband's name and date of birth; it's helpful to have his Social Security number, too, but not essential. The agency can retrieve it. Of course, your ex-husband must have paid into Social Security for at least 40 quarters, adds Zanca. Otherwise, you can't collect a benefit based on his record, even if you meet all the qualifications.